1. Field of Invention
This invention relates generally to the field of methods and apparatus for the repair of existing manholes and other like tubular structures and is more specifically directed to methods and apparatus involving sectioned panel assemblies and fillers of polymer based materials which can be pre-manufactured for installation within an existing manhole.
2. Description of the Prior Art
Deterioration of waste water system components is a severe and growing problem. Originally built of brick, block or concrete construction, these components develop leaks, cracks and holes due to age, erosion, corrosion and ground water intrusion. Leakage from old manholes and sewer lines contaminates the environment and sometimes result in catastrophic damage with respect to clean-up and repair costs. Over the course of time, settling or shifting of the earth around the manhole and/or the corrosive effects of harsh elements such as acids, alkalis and salts in the sewer or waste water cause degradation of the manholes, resulting in leakage or failure of the integrity of the manhole wall such that the sewage or waste water leaks into the environment. Repair or replacement of defective manholes is a constant problem facing government and private entities.
Since the cost of repairing the components is typically much less than the cost of replacement, many techniques have been developed to repair and rehabilitate waste water system components. For example, it is known to recast manholes and the like through the use of forms and poured concrete, such a shown in U.S. Pat. No. 5,032,197 to Trimble. Because this process is very labor intensive, many techniques are directed toward spray-applied liners. For example, Strong in U.S. Pat. No. 5,002,438 teaches the use of sprayed cement to form a liner inside the deteriorating structure. Spray-applied epoxy, acrylic or polyurethane liners are also known, as is the use of resin impregnated substrates, such as felt, as taught in U.S. Pat. No. 5,017,258 to Brown et al. The current spray-applied systems suffer from moisture, delamination, shrinkage and structural weakness problems resulting from the typical environment encountered in the repair operations. See also my pending application Ser. No. 08/126,376 filed on Sep. 24, 1993, which discloses a technique and device for rehabilitating or repairing waste water system components or the like, comprising a spray-applied, multilayer liner which seals the components and imparts structural integrity. The liner comprises a primer layer, a first moisture barrier layer, a foam layer and a second moisture barrier layer. The primer layer can be applied to wet surface and is the bonding layer between the waste waster system component, typically, a concrete or cement surface, and the first moisture barrier layer imparts structural strength and rigidity to the cured liner. Except for the primer layer, the layers of the liner are all rapid cure materials. Preferably, the primer layer is an epoxy, the moisture barrier layers are polyureas and isocynate blend, and the foam layer a polyurethane.
In addition, a number of solutions have been presented which involve the insertion or creation of liners into the manhole, the new liner providing the integrity to prevent loss of sewer or waste water to the environment. Such solutions in the past have dealt with directly applying a polymer resin, such as a polyester, epoxide, polyurethane or acrylic, to the inner wall of the manhole by troweling, brushing or spraying. This solution provides for a liner which has little structural or reinforcing strength. Another solution is to provide a continuously extruded tubular polymer lining. This solution is difficult to apply to manholes, being primarily directed at the horizontal conduit pipes, and likewise provides little structural and reinforcing attributes.
Another approach is to use a plural number of relatively rigid plastic sheets joined together to form a liner tube within the manhole. For example, U.S. Pat. No. 4,751,799 to Ditcher et al. This construction does not import any structural strength and the joints are susceptible to failure over time. U.S. Pat. No. 4,670,315 to Hillemeier et al discloses a concrete bonding layer placed between the liner and the manhole wall. Other known methods provide for anchoring members which extend into the concrete bonding layer and snap fit members at the joints between the panels, such as U.S. Pat. No. 5,168,682 to Rye. The use of concrete as a bonding layer, because of its significant weight, usually requires that a mandrel or form be used inside the plastic liner until the concrete hardens, since the plastic liner would have to be inappropriately thick to provide enough support on its own when the concrete is poured. Additionally, the use of concrete as the bonding layer means that all incoming water leaks into the manhole being repaired must be completely stopped prior to insertion of the concrete. This is a very labor and time intensive project, as each leak must be individually addressed, and in many cases the leaks are extremely difficult to control.